Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
n,m = map(int,input().split())
cnt = 0
grid = [list(input()) for i in range(n)]
grid2 = [[]]*n
for i in range(n):
  cnt += "".join(grid[i]).count("#")
  grid2[i] = ["#"] + grid[i] + ["#"]
  
grid2.insert(0,["#"]*(m+2))
grid2.append(["#"]*(m+2))
grid2[1][1] = 0
loc =[[1,1]]

for k in range(1,n*m):
  next_loc = []
  for y,x in loc:
    for i,j in ([-1,0],[1,0],[0,-1],[0,1]):
      if grid2[y+i][x+j] == ".":
        grid2[y+i][x+j] = k
        next_loc.append([y+i,x+j])
  loc = next_loc
#  print(loc,k)
  if [n,m] in loc:
    break

ans = n*m - (k+1+cnt)

print(ans if ans >= 0 else -1)